Such devices exhibit operating frequencies in the range of a few hundreds of KHz to a few GHz, and are used in wireless transmission systems, for example RF and microwave, in order to combine the power of two signals. For example, advanced amplifier architectures require this type of device in order to combine the amplified signals coming from multiple branches; these can notably be linear amplifiers using non-linear components (LING).
Generally speaking, a combiner is a device allowing two or more separate signals to be combined into a single signal. In the context of wireless systems, this device allows a set of signals to be combined as shown schematically in FIG. 1 in the case of RF signals. Depending on the architecture of the combiner, it is possible to obtain an isolation between the input ports. This isolation limits the influence and the effect of each branch on the other ports. Conventional combiners are made from discrete passive elements or transmission lines.
In the context of mobile wireless communications, such as mobile telephony, the dimensions of the circuits need to be miniaturised. However, the conventional solutions occupy a large volume and are difficult to miniaturise. For example, the solution with discrete components requires components of high values that are difficult to integrate owing to their resulting high losses. On the other hand, the transmission line solution, requires long lines depending on the electrical length. In the ranges of frequencies lower than a few GHz, these physical lengths required are greater than a centimeter and hence difficult to envisage in an integrated circuit.
There is therefore a pressing need to find solutions that can be integrated, in other words that can be miniaturised, in order to enable the development of numerous architectures requiring combinations of power, in particular RF power, for applications of the mobile telephony type and mobile wireless systems.